The conclusion to the Quatermass story stars John Mills as Bernard Quatermass and Simon MacCorkindale (MANIMAL) as his associate. The world is falling to chaos and many groups of young people start following a strange cult that abhors technology. They start gathering around ancient stone relics in England (and worldwide), where a bright light appears and zaps them. Thousands upon thousands of people are being killed like this, like Lemmings going over a cliff. Quatermass has a theory that an alien intelligence is behind it and is transporting their essence across space, for either food or entertainment. The people are incinerated but something is being harvested from them.

There's a few subplots going on, such as the destruction of a space station, Joe Kapp losing his family and Quatermass searching for his neice, who ran away to join one of these cults.

This is an engaging, sci-fi miniseries with some horrific overtones, definitely worth checking out.